Train control system



1943- F. H. NICHOLSON ET AL 2,332,248

TRAIN CONTROL SYSTEM Filed March 19, 1942' [JVVF/VZ'OHS. E an]: Ell 201200012 andZemZzPHAlgozz 721m ATTORNEY.

Patented Oct. 19, 1943 UNITED STATES PATENT OFF/ICE TRAIN CONTROL SYSTEM Company, Pennsylvania Swissvale, Pa.,

a corporation of Application Mm'h 19, 1942, Serial No. 435,254

8 Claims.

Our invention relates to train control systems, and more particularly to systems of the type in which a train is equipped with apparatus designed to be controlled attimes by coded trackway current and at other times by trackway current which is non-coded.

Systems are well known in which the traincarried apparatus is selectively responsive to trackway current coded at different frequencies to produce a plurality of indications on the train. One such system in which the train-carried apparatus is capable of displaying four distinctive indications including a clear indication is disclosed in United States Patent No. 1,986,679, granted to Lloyd V. Lewis on January 1, 1935.

his also well known to arrange the train carried apparatus so that it will respond also to uncoded trackway current by employing a train-carried modulator or coder which periodically varies the uncoded energy pickedup from thetrackway in such -a manner as to cause the display of a clear cab signal. One such system is shown in the United States Patent No. 2,160,668, granted to Frank H. Nicholson'on May 30, 1939.

Another such' system is shown in the United States Patent No. 2,160,669, granted to Leslie R. Allison on May 30, 1939, and'our present invention is an improvement on the system shown in this patent.

One object of our present invention is to render "theoperation of the modulator entirely free from interference by false rail currents or mechanical disturbances arising from sudden starting or stopping of the locomotive, or from other causes.

Another object of our invention is to accomplish the desired safe operation in a relatively simple and direct manner without the necessity for complicated checking apparatus. Other objects, purposes and advantages of our apparatus will become apparent from the description which follows; 1 s We accomplish the foregoing objects chiefly by employing a control relay C of the quick response type which controls a normally inoperative coder M maintained in its inoperative con dition through the application of energy thereto. Coding of the uncoded current picked up in the receiver is accomplished through the alternate periodic operation of relay C0 ;and coder M.

We shall describe one form of train control system embodying our invention, and shall then view showing one form of train-carried apparatus embodying our invention.

Referringcto the drawing, the, apparatus is generally similar to that shown in Fig. l of the Allison patent identified above and comprises a receiver R located in inductive relationwith the trackway so that codedcurrent having a carrier frequency of cycles per second and uncoded current having a frequency of cycles per second may be induced therein. These two frequencies correspond with values used in practice and are used herein to make the description more clear but it is understood that these values are illustrative only and that any two frequencies having the necessary separation for proper selective'response of the train-carried apparatus may beusecl as well. The receiver R is connected through a receiver circuit lwith the primary winding of a transformer Tl, the secondary of which forms part of a filter F and the output of which is delivered to the grid circuit of an MR is well known, this apparatus is not shown,

for simplicity. It is sufiicient for our purposes to point out that one form of cab signal apparatus which may be controlled by relay MR is that shown in the aforementioned Lewis patent. The filaments of the electron tubes El and E2 are supplied with energy from the terminals B32 and C oia suitable unidirectional current source, not shown, which may be the usual dynamotor energized from the locomotive headlight generator. The plate circuits of these tubes are supplied from asuitable source of high potential unidirectional current having the terminals B300 and C which source may likewise be a dynamotor winding.

The train-carried apparatus also includes a cut-over switch S which will usually be, operated by, the engineman and which is arranged when The receiver circuit 1 is tuned by means of the series combination of condensers 2 and to substantial resonance at the frequency of the noncoded current, assumed to be 140 cycles per second, and the filter F is also tuned to substantial resonance at this frequency by means of condenser 3. When the switch S is in the code position, as shown, contact 4 of the switch shortcircuits condenser 5 to tune the receiver circuit to substantial resonance at the frequency of the coded current which has been assumed to be 106 cycles per second. Under this condition, switch contacts 6 and 8 at the same time connect the condenser in parallel with condenser 3 in the filter circuit to tune the filter to substantial resonance at the frequency of the coded current, or 160 cycles.

Accordingly, with the switch S in the position illustrated, coded current induced in the receiver R is supplied through the receiver circuit I and the filter F to the first stage tube El and after being amplified and detected by the tube E2, operates the master relay MR at code frequency, that is, at the frequency of the code variations in the trackway current. If these code variations occur at clear code frequency, then relay MR. will cause a clear cab signal to be displayed. It will be noted that with the cutover switch S occupying the code position as illustrated, the control relay 00 has its operating winding short-circuited over contact 9 of the switch S and wire It). Relay CO is a sensitive, quick acting relay capable of following the code impulses of clear code frequency. When released as shown, relay CO has its back contact ii closed so as to maintain the coder M constantly energized whereby the coder contacts l2 and i3 are held constantly open due to the fact that the movable element of the coder is held firmly in the contact open position at one end of its stroke. This coder may be of the mechanically tuned type shown in the United States Patent No. 1,358,876, granted to Paul N. Bossart on May 17, 1932, with the exception that the driving contact is omitted whereby the application of energy does not cause the movable element of the coder to oscillate, butcauses it to be held firmly in the position in which the coder contacts are open. This coder is so designed that after its energizing circuit is interrupted, it will oscillate or coast through a number of cycles, closing the contacts l2 and 13 a number of times, before coming to rest. The purpose of the rectifier I4 is to serve as a spark arrester.

From the description presented so far, it will be clear that with the switch S in the position shown for operation in code territory, relay CO is released, coder M is maintained inoperative by energy constantly applied thereto, and the apparatus is tuned to the carrier frequency of the coded current so that the master relay MB is responding to code impulses.

We shall now assume that the train has entered non-code territory and the engineman has moved the switch S to its dotted line position. In this position, contact 4 removes the shunt from around condenser 5 so that the receiver circuit becomes tuned to 140 cycles which is the frequency of the uncoded current. Likewise, switch contact 6 disconnects condenser 1 so that the filter is now tuned to 140 cycles. However, up to this point, no code variations are impressed on the current which has been picked up from the trackway. These code variations are introduced into the receiver and filter circuits through the cooperation of the control relay C0 and the coder M in a manner which will now be described.

The relay CO has an energizing circuit which includes the primary winding of transformer T3 in the plate circuit of tube 122. When 140 cycle current of a predetermined amount flows under the receiver R, and switch contact 9 has been opened to remove the short-circuit from across relay CO, this relay is picked up by the steady flow of second stage plate current through its operating winding. This causes back contact ii to open so as to deenergize the mechanically tunedcoder M and allow its contacts l2 and Hi to close momentarily during the back swing of the coder movable element or armature, thus momentarily detuning the apparatus from its previous condition of resonance to current or" 140 cycle frequency. As will be clear from the drawing, contact l2 shunts out the condenser 5 in the receiver input circuit and reconnects the condenser l in the filter circuit, thus changing the tuning from l lO cycles to, cycles. Obviously, the impedance of the apparatus to current of cycles when the. receiver and filter are tuned to 100 cycles is very high so that the second stage plate current is, in effect, cut oil whereupon relay CO momentarily releases.

The release of relay CO closes contact Ii, reenergizing coder M which opens contacts l2 and i3 and retunes the apparatus to 140 cycles. hereupon, relay CO receives another operating impulse and the cycle is repeated periodically. Since the coder M is mechanically tuned to have a definite natural frequency which can be assumed to correspond with the frequency of the clear code variations such as cycles per minute for purposes of illustration, in coasting it will operate at this frequency and in so doing, will take. control and determine the frequency at which relay CO picks up and releases. We have found by experiment that best results are obtained when the angular movement of the coder armature between its steadily energized and steadily deenergized positions is the largest possible, as limited by the condition that the armature must notfail to pull in to its energized position when relay CO is released and contact I l closes.

It will be apparent from the foregoing description that with the switch S in the non-code position and with trackway current of the 140 cycle frequency being picked up by the receiver, relay CO and coder M will operate alternately at the frequency to which the coder is mechanically tuned, thereby impressing the required code variations on the 140 cycle'current in the receiver circuit. The master relay MR will respond to these code variations and will provide the same operation as. that obtained in coded territory with the switch S in its code position. Accordingly, with onlya change in the position of the cutovcr switch, the same train-carried apparatus is capable of providing a clear cab signal indication in non-code territory as well as in code territory. 7 I I It will be understood that although we prefer to use coded and-uncoded currents, the apparatus is not limited to such use but may be used with modified and unmodified currents generally, the important consideration being that the apparatus should change the unmodified receiver current so that it simulates the modified current in the desired respect.

Considering further the operation of the apcircuits.

paratus in non-code territory, w'e have found that at relatively high values of 140 cycle cur rent in the trackway, the energy which is stored in the relay CO is sufficiently great to prevent quick release of this relay as soon as the coder contacts l2 and Ill-become closed. Under this condition, it is impossible for the coder to' force relay CO to maintain approximately equal on andfo-fi periods so that undesired distortion of the code received by relay MR could result. To overcome this difliculty, we have provided an automatic bias control feature for tube E2 comprising'a condenser l5 and resistor l6 connected in parallel with one another into the second stage grid circuit. This bias control feature is well value of trackway currentjust sufiicient for pickup of relay CO and values of. this current many times greater. a

One difiiculty which train control apparatus of the, composite code and non-code type using a train-carried coder shouldavoid is that resulting from false energization of thereceiver or tube since the coder M must be'energized not constantly but intermittently, at or near the frequency to which it ismechanically tuned, and the energizing impulses must 'recur in proper phase relation to one another, the coder'M'isincapable of coding the input circuits to provide a clear indication except when 140 cycle current is present in the trackway. This important safety. feature has been thoroughly demonstrated in practical operation of the apparatus.

Although the automatic bias control apparatus is not seriously objectionable during 100 cycle operation in code. territory, we prefer to shortcircuit the resistor-condenser combination over wire H and a switch contact 8 when the cutover switch is in its. code position, as illustrated.

In this way, we preventthe somewhat higher;

ratio of pick-up at .100 cycles to that at 140 cycles which would be effective if the bias control re' mained in the "circuit during 100.cycle operation.

Although we have herein shown and described only one form of a train control system embodying our invention, it is understood that various 1 changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim is: I

1. In a train control system, the combination with a receiver to be energized by modified or unmodified periodic current flowing in the trackway and a traffic control device supplied with energy from said receiver and responsive to the influence of modified current, of a control relay energized in response to the flow of said unmodified current but not said modified current If the tube input circuits are falsely energized through accidental leakage or capacity in said receiver, a coder having a tuning contact, an energizingcircuit for said coder including a back contact of said control relay to maintain saidcoder inoperative and said tuning contact .open,whereby when said control relay is'cnergized and saidback contact becomes opened said coder will be 'deenergized and will momentarily close said tuning contact, and means controlled by said tuningcontact when closed for modifying the current in said receiver to thereby cause a release of said control relay, whereby when unmodified current flows in the trackway said control relay and said coder will operate alternately to periodically modify the current in said receiver and so to cause response of said traflic control device.

2. In a train control system, the combination with a receiver to be energized by modified current'of one frequency or unmodified current of another frequency flowing in the trackway and a traiiic control device supplied with energy from saidreceiver and responsive to the influence oi modified'current, of a control relay energized in response to the flow of unmodified current in said receiver, a switching device having a first position corresponding with the flow of modified current in said receiver and a second position corresponding with the flow of unmodified current in said receiver, means effective when said switching device is in said first position for preventing energization of said control relay and for tuning said receiver to the frequency of said modified current, means effective when said switching device is in said secondposition for tuning saidreceiver to the frequency or said unmodified current to thereby permit energization of said control relay, a coder having an energizing circuit including a back contact of said control relay, a contact operated by said code: which remains open when the coder is energized but which is momentarily closed upon deenergization of said coder, and means controlled by said coder contact effective when said switching device in said second position for detuning said receiver to thereby cause a release'of said control relay, whereby'when unmodified current flows in the trackway and said switching device occupies said second position said control relay and said coder will operate'alternately to periodically modify the current in said receiver and so to cause response ofsaid trafiic control device.

3. In a train control system, the combination with a receiver to be energized by coded or uncoded periodic current flowing in the trackway and a traffic control device responsive to the infiuence of said coded current but nct said until) coded current, a control relay energized in re sponse to the flow of said uncoded current in said receiver, a coder having an energizing circuit including a back contact of said control relay for maintaining said coder inoperative, and meanscontrolled by said coder effective when said relay is energized and said coder is deenergized for momentarily decreasing the current in said'receiver to alternately and periodically deenergize said control relay and energize said coder, whereby the uncoded current in said receiver is periodically decreased to simulate coded current and cause response of said traffic control device.

4. In a train control system, the combination with a receiver to be energized by coded or uncoded periodic current flowing in the trackway and a traffic control device responsive to the influence of said coded current but not said uncoded current, a control relay energized in re sponse to the flow of said uncocled current said receiver, means for, preventing energizatlon of said control relay when coded current flows in said receiver, a coder having an energizing circuit including a back contact of said control relay for maintaining said coder inoperative, and means controlled by said codereifective when said relay is energized for momentarily coding the current in said receiver to alternately and periodically deenergize said control relay and energize said coder, whereby the current in said receiver is periodically coded to cause response of said traffic control device.

5. In a train control system, the combination with a receiver to be energized by coded or uncoded periodic current flowing in the trackway and a traffic control device responsive to the infiuence of said coded current but not said uncoded current, a control relay energized in response to the flow of said uncoded current in said receiver, a switching device having a first position corresponding with the flow of coded current in said receiver and a second position corresponding with the flow of uncocled current in said re ceiver, a first contact operated by said switching device and effective when and only when said switching device is in said first position for pre venting energization of said control relay, a coder having an energizing circuit including a bacl-z contact of said control relay for maintaining said coder inoperative, means controlled by said coder effective when said relay is energized and said coder is deenergized for momentarily decreasing the current in said receiver to alternately deener-- gize said relay and energize said coder, said alternate operation continuing periodically as long as uncoded current flows in said receiver and said switching device is in said second position, ther by simulating said coded current to cause response of said trafiic control device, and a second contact operated by said' switching device when in said first position for rendering said m ans ineffective to decrease said receiver current.

6. In a train control system, the combination with a receiver to be energized by coded current of a first frequency or uncocled current of a second frequency flowing in the trackway and a traffic control device responsive to the influence of said coded current but not said uncocled current, manually operable means having a first position for tuning said receiver to said coded current to operate said traific control device and having a second position for tuning said receiver to said uncocled current, a control relay energized in response to the now of said uncoded current in said receiver when the receiver is tuned thereto by said means, a coder having an energizing circuit including a back contact of said control relay for maintaining said coder inoperative, and means controlled by said coder effective when said relay is energized and said coder is deenergized for momentarily detuning said receiver to alternately and periodically deenergize said controlrelay and energize said coder, whereby said uncoded current in said receiver is peri-- odically changed to simulate said coded current "and cause response of said trafiic control device.

'7. In a train control system, the combination with a receiver to be energized by coded current of a first frequency or uncocled current of a second frequency flowing in the trackway and a trafiic control device responsive to the influence of said coded current but not said uncocled current, a manually operable device having a first position for tuning said receiver to said coded.

current to cause response of said trafdc control device and having a second position for tuning said receiverto said uncocled current, a control relay energized in response to the flow of said uncocled current in said receiver when the receiver is tuned thereto by said device, means effective when said device is in said first position for pre venting energization of said control relay, a coder mechanically tuned to the frequency of code variations of said coded current, an energizing circuit for said coder including aback contact of said, control relay for maintaining said coder inoperative, and means controlled by said coder effective when said relay is energized and said cooler is deenergized for momentarily detuning said re ceiver to alternately'and periodically deenergize said control relay and energize said coder, whereby said uncoded current in said receiver is periodically changed to simulate said coded current and cause response of said trafiic control device.

3. In a train control system, the combination with a receiver to be energized by coded or uncocled periodic current flowing in the traclzway, an amplifier and a traffic governing device controlled by said amplifier in response to said coded current but not said uncocled current, circuit means for connecting, said receiver with the input terminals of said amplifier, a quick-response control relay energized from the output of said an plifier in response to the fiow of said uncoded current in said receiver, a coder having an energizing circuit including a back contact of said control relay for maintaining said coder inoperative, means controlled by said coder effective when said control relay is energized and said coder is deenergized for momentarily decreasing the current in said receiver to alternately and periodically deenergize said control relay and energize said coder, whereby the uncocled current in said receiver is periodically decreased to simulate said coded current and cause response of said traffic governing device, and means associated with said amplifier for preventing over-energization of said control relay due to high receiver current to thereby simulate said coded current without updue distortion.

FRANK H. NICHOLSON. LESLIE R. ALLISON 

